arXiv subjects

H. Sundu

Publications and source records attributed to H. Sundu.

At least 91 records · Page 5Linked to original sources

arXiv2019

Light scalar $K_{0}^{*}(700)$ meson in vacuum and a hot medium

The $K_{0}^{*}(700)$ meson appears as the lightest strange scalar meson in PDG. Although there were a lot of experimental and theoretical efforts to establish this particle and determine its properties and nature, it still needs confirmation in an experiment and its internal quark-gluon organization needs to be clarified. In this connection, we study some spectroscopic properties of this state in a hot medium as well as a vacuum by modeling it as a usual meson of a quark and an aniquark. In particular, we investigate its mass and coupling or decay constant in terms of the temperature of a hot medium by including the medium effects by the fermionic and gluonic parts of the energy momentum tensor as well as the temperature-dependent continuum threshold, quark, gluon and mixed condensates. We observe that the mass of $K_{0}^{*}(700)$ remains unchanged up to $T \simeq 0.6 ~ T_c$ with $ T_c $ being the critical temperature, but it starts to diminish after this point and approaches zero near to the critical temperature referring to the melting of the meson. The coupling of $K_{0}^{*}(700)$ is also sensitive to $ T $ at higher temperatures. It starts to grow rapidly after $T \simeq 0.85 ~ T_c$. We turn off the medium effects and calculate the mass and coupling of the $K_{0}^{*}(700)$ state at zero temperature. The obtained mass is in accord with the average Breit-Wigner mass value reported by PDG.

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arXiv2019

Decay modes of the scalar exotic meson $T_{bs;\overline{u}\overline{d}}^{-}$

We investigate the semileptonic decay of the scalar tetraquark $T_{bs; \overline{u}\overline{d}}^{-}$ to final state $T_{cs;\overline{u}\overline{d} }^{0} l \overlineν_l$, which proceeds due to the weak transition $b \to c l \overlineν_l$. For these purposes, we calculate the spectroscopic parameters of the final-state scalar tetraquark $T_{cs;\overline{u}\overline{ d}}^{0}$. In calculations we use the QCD sum rule method by taking into account the quark, gluon, and mixed condensates up to dimension 10. The mass of the $T_{cs;\overline{u}\overline{d}}^{0}$ obtained in the present work $( 2878 \pm 128 )~\mathrm{MeV}$ indicates that it is unstable against the strong interactions, and can decay to the mesons $D^{0}\overline{K}^{0}$ and $D^{+}K^{-}$. Partial widths of these $S$-wave modes as well as the full width of the tetraquark $T_{cs;\overline{u}\overline{d}}^{0}$ are found by means of the QCD light-cone sum rule method and technical tools of the soft-meson approximation. The partial widths of the main semileptonic processes $T_{bs;\overline{u}\overline{d}}^{-} \to T_{cs;\overline{u} \overline{d}}^{0}l\overlineν_l$, $l=e, μ$, and $τ$ are computed by employing the weak form factors $G_{1}(q^2)$ and $G_{2}(q^2)$, which are extracted from the QCD three-point sum rules. We also trace back the weak transformations of the stable tetraquark $T_{bb;\overline{u}\overline{d} }^{-} $ to conventional mesons. The obtained results for the full width $ Γ_{\mathrm{full}}=(3.28\pm 0.60) \times 10^{-10}~\mathrm{MeV} $ and mean lifetime $τ=2.01_{-0.31}^{+0.44}~\mathrm{ps}$ of $T_{bs;\overline{u} \overline{d}}^{-}$, as well as predictions for decay channels of the tetraquark $T_{bb;\overline{u}\overline{d}}^{-}$ can be used in experimental studies of these exotic states. \end{abstract}

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arXiv2019

Double-heavy axial-vector tetraquark $T_{bc;\bar{u}\bar{d}}^{0}$

The mass and coupling of the axial-vector tetraquark $T_{bc;\bar{u}\bar{d} }^{0}$ (in a short form $T_{bc}^{0}$) are calculated by means of the QCD two-point sum rule method. In computations we take into account contributions arising from various quark, gluon and mixed vacuum condensates up to dimension 10. The central value of the mass $m=(7105 \pm 155)~\mathrm{ MeV}$ lies below the thresholds for the strong and electromagnetic decays of $T_{bc}^{0}$ state, and hence it transforms to conventional mesons only through the weak decays. In the case of $m=7260~\mathrm{MeV}$ the tetraquark $T_{bc}^{0}$ becomes the strong- and electromagnetic-interaction unstable particle. In the first case, we find the full width and mean lifetime of $ T_{bc}^{0}$ using its dominant semileptonic decays $T_{bc}^{0}\to T_{cc;\bar{ u}\bar{d}}^{+}l\overline{ν}_{l}$ ($l=e,\ μ, τ$), where the final-state tetraquark is a scalar state. We compute also partial widths of the nonleptonic weak decays $T_{bc}^{0}\to T_{cc;\bar{u}\bar{d} }^{+}π^{-}(K^{-}, D^{-}, D_{s}^{-})$, and take into account their effects on the full width of $T_{bc}^{0}$. In the context of the second scenario we calculate partial widths of $S$-wave strong decays $T_{bc}^{0}\to B^{\ast -}D^{+}$ and $T_{bc}^{0}\to \overline{B}^{\ast 0}D^{0}$, and using these channels evaluate the full width of $T_{bc}^{0}$. Predictions for $Γ_{ \mathrm{full}} =(3.98\pm 0.51)\times 10^{-10}~\mathrm{MeV}$ and mean lifetime $τ=1.65_{-0.18}^{+0.25}~\mathrm{ps}$ of $T_{bc}^{0}$ obtained in the context of the first option, as well as the full width $Γ_{\mathrm{ full}}=(63.5\pm 8.9)~\mathrm{MeV}$ extracted in the second scenario may be useful for experimental and theoretical exploration of double-heavy exotic mesons.

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arXiv2019

Semileptonic decays of the scalar tetraquark $Z_{bc;\overline{u} \overline{d}}^{0}$

We study semileptonic decays of the scalar tetraquark $Z_{bc;\overline{u} \overline{d}}^{0}$ to final states $T_{bs;\overline{u}\overline{d} }^{-}e^{+}ν_{e}$ and $T_{bs;\overline{u}\overline{d}}^{-}μ^{+}ν_μ$ , which run through the weak transitions $c\to se^{+}ν_{e}$ and $c\to sμ^{+}ν_μ$, respectively. To this end, we calculate the mass and coupling of the final-state scalar tetraquark $T_{bs;\overline{u}\overline{d} }^{-} $ by means of the QCD two-point sum rule method: these spectroscopic parameters are used in our following investigations. In calculations we take into account the vacuum expectation values of the quark, gluon, and mixed operators up to dimension ten. We use also three-point sum rules to evaluate the weak form factors $G_{i}(q^2)$ ($i=1,~2$) that describe these decays. The sum rule predictions for $G_{i}(q^2)$ are employed to construct fit functions $F_{i}(q^2)$, which allow us to extrapolate the form factors to the whole region of kinematically accessible $q^2$. These functions are required to get partial widths of the semileptonic decays $Γ\left( Z_{bc}^{0}\rightarrow Te^{+}ν_{e}\right) $ and $Γ\left( Z_{bc}^{0}\rightarrow Tμ^{+}ν_{μ}\right)$ by integrating corresponding differential rates. We analyze also the two-body nonleptonic decays $Z_{bc;\overline{u}\overline{d}}^{0} \to T_{bs;\overline{u}\overline{d }}^{-}π^{+}$ and $Z_{bc;\overline{u}\overline{d}}^{0} \to T_{bs;\overline{u }\overline{d}}^{-}K^{+}$, which are necessary to evaluate the full width of the $Z_{bc;\overline{u}\overline{d}}^{0}$. The obtained results for $Γ_{ \mathrm{full}}=(3.18\pm 0.39)\times 10^{-11}~\mathrm{MeV}$ and mean lifetime $20.7_{-2.3}^{+2.9}~\mathrm{ps}$ of the tetraquark $Z_{bc;\overline{u} \overline{d}}^{0}$ can be used in experimental investigations of this exotic state.

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arXiv2019

Light axial-vector and vector resonances $X(2100)$ and $X(2239)$

We study features of the resonances $X(2100)$ and $X(2239)$ by treating them as the axial-vector and vector tetraquarks with the quark content $ss \overline{s}\overline{s}$, respectively. The spectroscopic parameters of these exotic mesons are calculated in the framework of the QCD two-point sum rule method. Obtained prediction for the mass $m=(2067 \pm 84)~\mathrm{MeV}$ of the axial-vector state is in excellent agreement with the mass of the structure $X(2100)$ recently observed by the BESIII Collaboration in the decay $J/ψ\to ϕηη^{\prime}$ as the resonance in the $ϕη^{\prime}$ mass spectrum. We explore also the $S$-wave decays $X(2100) \to ϕη^{\prime}$ and $X(2100) \to ϕη$ using the QCD light-cone sum rule approach and technical methods of the soft-meson approximation. The width of the axial-vector tetraquark, $Γ=(130.2\pm 30.1)~\mathrm{MeV}$, saturated by these two decays is comparable with the measured full width of the resonance $X(2100)$. Our prediction for the vector $ss\overline{s}\overline{s }$ tetraquark's mass $\widetilde{m}=(2283\pm 114)~\mathrm{MeV}$ is consistent with the experimental result $2239.2 \pm 7.1 \pm 11.3~\mathrm{MeV}$ of the BESIII Collaboration for the mass of the resonance $X(2239)$.

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arXiv2019

Lepton flavor universality violation in semileptonic tree level weak transitions

The recent deviations of the experimental data on some parameters of the tree-level semileptonic $B$ and $B_c$ mesons decays from the standard model (SM) predictions indicate considerable violations of the lepton flavor universality, and as a result possible new physics (NP) effects. To better understand the possible NP effects it is necessary to study deeply the physical quantities defining these decays from many aspects. The calculations of the physical quantities require the determinations of the hadronic form factors entering the matrix elements of the considered transitions as the main inputs. We calculate the form factors governing the tree-level $B_c\rightarrow J/ψl ν$ and $B_c \rightarrow η_c l ν$ transitions within the QCD sum rules method. The obtained form factors are used in the calculations of the branching ratios ($BR$s) of the $B_c \rightarrow J/ψl ν$ and $B_c \rightarrow η_cl ν$ transitions as well as $R(J/ψ)$ and $R(η_c)$. Our result on $R(J/ψ)$ supports the present tension between the SM theory prediction and the experimental data. Our result on $R(η_c)$ can be checked in future experiments.

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arXiv2019

Strong decays of double-charmed pseudoscalar and scalar $cc\overline{u}\overline{d}$ tetraquarks

The strong decays of the pseudoscalar and scalar double-charmed tetraquarks $ T_{cc;\overline{u}\overline{d}}^{+}$ and $\widetilde{T}_{cc;\overline{u} \overline{d}}^{+}$ are investigated in the framework of the QCD sum rule method. The mass and coupling of these exotic four-quark mesons are calculated in the framework of the QCD two-point sum rule approach by taking into account vacuum condensates of the quark, gluon, and mixed local operators up to dimension 10. Our results for masses $m_{T}=(4130~\pm 170)~ \mathrm{MeV} $ and $m_{\widetilde{T}}=(3845~\pm 175)~\mathrm{MeV}$ demonstrate that these tetraquarks are strong-interaction unstable resonances and decay to conventional mesons through the channels $T_{cc; \overline{u}\overline{d}}^{+} \to D^{+}D^{\ast }(2007)^{0},~D^{0}D^{\ast }(2010)^{+}$ and $\widetilde{T}_{cc;\overline{u}\overline{d}}^{+}\to D^{+}D^{0}$. Key quantities necessary to compute the partial width of these decay modes, i.e., the strong couplings of two $D$ mesons and a corresponding tetraquark $g_i,~i=1,2$, and $G$ are extracted from the QCD three-point sum rules. The full width $Γ_{T}=(129.9\pm 23.5)~\mathrm{ MeV}$ demonstrates that the tetraquark $T_{cc;\overline{u}\overline{d}}^{+}$ is a broad resonance, whereas the scalar exotic meson with $Γ_{ \widetilde{T}}=(12.4\pm 3.1)~\mathrm{MeV}$ can be classified as a relatively narrow state.

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arXiv2019

Determination of the quantum numbers of $Σ_b(6097)^{\pm}$ via their strong decays

The progresses in the experimental sector have been the harbinger of the observations of many new hadrons. Very recently, LHCb Collaboration announced the observation of two new $Σ_b(6097)^{\pm}$ states in the $Λ^0_bπ^{\pm}$ invariant mass distribution, which are considered as the excited states of the ground state $Σ^{(*)}_b$ baryon. Though, almost all of the ground state baryons have been observed, having a limited number of excited states observed so far makes them intriguing. Understanding the properties of the excited baryons improve our knowledge on the strong interaction as well as the nature and internal structures of these baryons. To specify the quantum numbers of the $Σ_b(6097)^{\pm}$ an analysis on their strong decays to $Λ_b^0$ and $π^{\pm}$ is performed within the light cone QCD sum rule formalism. To this end, they are considered as possible $1P$ or $2S$ excitation of either the ground state $Σ_b$ baryon with $J=\frac{1}{2}$ or $Σ_b^{*}$ baryon with $J=\frac{3}{2}$. The corresponding masses are also calculated considering the same scenarios for their quantum numbers. The results of the analyses indicate that the $Σ_b(6097)^{\pm}$ baryons are excited $1P$ baryons having quantum numbers $J^P=\frac{3}{2}^-$.

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arXiv2019

New charged resonance $Z_{c}^{-}(4100)$: the spectroscopic parameters and width

The mass, coupling and width of the newly observed charged resonance $ Z_{c}^{-}(4100)$ are calculated by treating it as a scalar four-quark system with a diquark-antidiquark structure. The mass and coupling of the state $ Z_{c}^{-}(4100)$ are calculated using the QCD two-point sum rules. In these calculations we take into account contributions of the quark, gluon and mixed condensates up to dimension ten. The spectroscopic parameters of $ Z_{c}^{-}(4100)$ obtained by this way are employed to study its $S$-wave decays to $η_c(1S)π^{-}$, $η_c(2S)π^{-}$, $D^{0}D^{-}$, and $ J/ψρ^{-}$ final states. To this end, we evaluate the strong coupling constants corresponding to the vertices $Z_{c}η_c(1S)π^{-}$, $ Z_{c}η_c(2S)π^{-}$, $Z_{c}D^{0}D^{-}$, and $Z_{c}J/ψρ^{-}$ respectively. The couplings $g_{Z_cη_{c1} π}$, $g_{Z_{c}η_{c2} π}$ , and $g_{Z_{c}DD}$ are computed by means of the QCD three-point sum rule method, whereas $g_{Z_{c}J/ψρ}$ is obtained from the QCD light-cone sum rule approach and soft-meson approximation. Our results for the mass $ m=(4080 \pm 150)~\mathrm{MeV}$ and total width $Γ=(147 \pm 19)~\mathrm{ MeV}$ of the resonance $Z_{c}^{-}(4100)$ are in excellent agreement with the existing LHCb data.

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arXiv2019

Weak decays of the axial-vector tetraquark $T_{bb;\bar{u} \bar{d}}^{-}$

The weak decays of the axial-vector tetraquark $T_{bb;\bar{u} \bar{d}}^{-}$ to the scalar state $Z_{bc;\bar{u} \bar{d}}^{0}$ are investigated using the QCD three-point sum rule approach. In order to explore the process $T_{bb; \bar{u} \bar{d}}^{-} \to Z_{bc;\bar{u} \bar{d}}^{0}l \bar{ν_l}$, we recalculate the spectroscopic parameters of the tetraquark $T_{bb;\bar{u} \bar{d}}^{-}$ and find the mass and coupling of the scalar four-quark system $Z_{bc;\bar{u} \bar{d}}^{0}$, which are important ingredients of calculations. The spectroscopic parameters of these tetraquarks are computed in the framework of the QCD two-point sum rule method by taking into account various condensates up to dimension ten. The mass of the $T_{bb;\bar{u} \bar{ d}}^{-}$ state is found to be $m=(10035~\pm 260)~\mathrm{MeV}$, which demonstrates that it is stable against the strong and electromagnetic decays. The full width $Γ$ and mean lifetime $τ$ of $T_{bb;\bar{u} \bar{d} }^{-}$ are evaluated using its semileptonic decay channels $T_{bb; \bar{u} \bar{d}}^{-} \to Z_{bc;\bar{u} \bar{d}}^{0}l \bar{ν_l}$, $l=e,μ$ and $τ$. The obtained results, $Γ=(7.17\pm 1.23)\times 10^{-8\ \ } \mathrm{MeV}$ and $τ=9.18_{-1.34}^{+1.90}~\mathrm{fs}$, can be useful for experimental investigations of the doubly-heavy tetraquarks.

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arXiv2019

The nonet of the light scalar tetraquarks: the mesons $a_0(980)$ and $K_{0}^{\ast }(800)$

The spectroscopic parameters and partial decay widths of the light mesons $ a_0(980) $ and $K_{0}^{\ast}(800)$ are calculated by treating them as scalar diquark-antidiquark states. The masses and couplings of the mesons are found in the framework of QCD two-point sum rule approach. The widths of the decay channels $a_0(980) \to ηπ$ and $a_0(980) \to K \bar{K}$, and $ K_{0}^{\ast}(800) \to K^{+} π^{-}$ and $K_{0}^{\ast}(800) \to K^{0} π^{0} $ are evaluated using QCD sum rules on the light-cone and technical tools of the soft meson approximation. Our results for the mass of the mesons $m_{a_0}=991^{+29}_{-27} \ \mathrm{MeV}$ and $m_{K^{ \ast}}=767^{+38}_{-29} \ \mathrm{MeV}$, as well as their total width $Γ_{\mathrm{a_0}}=62.01\pm 14.37\ \mathrm{MeV}$ and $Γ_{\mathrm{ K_0^{\ast}}}=401.1\pm 87.1\ \mathrm{MeV}$ are compared with last experimental data.

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arXiv2018

The doubly charmed pseudoscalar tetraquarks $T_{cc;\bar{s} \bar{s}}^{++}$ and $T_{cc;\bar{d} \bar{s}}^{++}$

The mass and coupling of the doubly charmed $J^P=0^{-}$ diquark-antidiquark states $T_{cc;\bar{s} \bar{s}}^{++}$ and $T_{cc;\bar{d} \bar{s}}^{++}$ that bear two units of the electric charge are calculated by means of QCD two-point sum rule method. Computations are carried out by taking into account vacuum condensates up to and including terms of tenth dimension. The dominant $S$-wave decays of these tetraquarks to a pair of conventional $ D_{s}^{+}D_{s0}^{\ast +}(2317)$ and $D^{+}D_{s0}^{\ast +}(2317)$ mesons are explored using QCD three-point sum rule approach, and their widths are found. The obtained results $m_{T}=(4390~\pm 150)~\mathrm{MeV}$ and $Γ=(302 \pm 113~\mathrm{MeV}$) for the mass and width of the state $T_{cc;\bar{ s} \bar{s}}^{++}$, as well as spectroscopic parameters $\widetilde{m} _{T}=(4265\pm 140)~\mathrm{MeV}$ and $\widetilde{Γ}=(171~\pm 52)~ \mathrm{MeV}$ of the tetraquark $T_{cc;\bar{d} \bar{s}}^{++}$ may be useful in experimental studies of exotic resonances.

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arXiv2018

Structure of the $Ξ_b(6227)^-$ Resonance

We explore the recently observed $Ξ_b(6227)^{-}$ resonance to fix its quantum numbers. To this end, we consider various possible scenarios: It can be considered as either 1P/2S excitations of the $Ξ_b^-$ and $Ξ_b'(5935)^{-}$ ground state baryons with spin-$\frac{1}{2}$ or 1P/2S excitations of the ground state $Ξ_b(5955)^{-}$ with spin-$\frac{3}{2}$. We calculate the masses of the possible angular-orbital $1P$ and $2S$ excited states corresponding to each channel employing the QCD sum rule technique. It is seen that all the obtained masses are in agreement with the experimentally observed value, implying that the mass calculations are not enough to distinguish the quantum numbers of the state under question. Therefore, we extend the analysis to investigate the possible decays of the same excited states into $Λ_b^0 K^-$ and $Ξ_b^-π$. Using the light cone QCD sum rule method, we calculate the corresponding strong coupling constants, which are used to extract the decay widths of the modes under consideration. Our results on decay widths indicate that the $Ξ_b(6227)^{-}$ is $1P$ angular-orbital excited state of the $Ξ_b(5955)^{-}$ baryon with quantum numbers $J^P=\frac{3}{2}^{-}$.

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arXiv2018

Nature of the $Ω$(2012) through its strong decays

We extend our previous analysis on the mass of the recently discovered $Ω(2012)$ state by investigation of its strong decays and calculation of its width employing the method of light cone QCD sum rule. Considering two possibilities for the quantum numbers of $Ω(2012)$ state, namely $1P$ orbital excitation with $J^P=\frac{3}{2}^-$ and $2S$ radial excitation with $J^P=\frac{3}{2}^+$, we obtain the strong coupling constants defining the $Ω(1P/2S)\rightarrowΞK$ decays. The results of the coupling constants are then used to calculate the decay width corresponding to each possibility. Comparison of the obtained results on the total widths in this work with the experimental value and taking into account the results of our previous mass prediction on the $Ω(2012)$ state, we conclude that this state is $1P$ orbital excitation of the ground state $Ω$ baryon, whose quantum numbers are $J^P=\frac{3}{2}^-$.

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arXiv2018

Resonance $Y(4660)$ as a vector tetraquark and its strong decay channels

The spectroscopic parameters and partial widths of the strong decay channels of the vector meson $Y(4660)$ are calculated by treating it as a bound state of a diquark and antidiquark. The mass and coupling of the $J^{PC}=1^{--}$ tetraquark $Y(4660) $ are evaluated in the context of the two-point sum rule method by taking into account the quark, gluon and mixed condensates up to dimension 10. The widths of the $Y(4660)$ resonance's strong $S$-wave decays to $J/ψf_{0}(980)$ and $ψ(2S) f_{0}(980)$ as well as to $ J/ψf_{0}(500)$ and $ψ(2S) f_{0}(500)$ final states are computed. To this end, strong couplings in the relevant vertices are extracted from the QCD sum rule on the light cone supplemented by the technical methods of the soft approximation. The obtained result for the mass of the resonance $ m_Y=4677^{+71}_{-63}\ \mathrm{MeV}$ and the prediction for its total width $ Γ_{Y}= (64.8 \pm 10.8)\ \mathrm{MeV}$ is in nice agreement with the experimental information.

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arXiv2018

Possible Molecular Pentaquark States with Different Spin and Quark Configurations

We investigate three possible pentaquark candidates, one of which contains a single charm quark and the other two contain triple charm quarks in their substructure. To this end we apply QCD sum rule method and take into account both the positive and negative parity states corresponding to each possible pentaquark channel having spin $3/2$ or $1/2$. Insisting on the importance of identification of the members of pentaquark family we obtain their spectroscopic parameters such as masses and residues. These parameters are the main inputs in the searches for their electromagnetic, strong and weak interactions.

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arXiv2018

On the nature of $Ξ_c(2930)$

The single charmed excited $Ξ_c(2930)$ state was discovered many years ago by BABAR collaboration and recently confirmed by Belle experiment. However, both of these experiments, unfortunately, could not fix the quantum numbers of this particle and its nature is under debates. In the present study, we calculate its mass and width of its dominant decay to $ Λ_c K $. To this end we consider $Ξ_c(2930)$ state once as angularly excited and then radially excited single charmed baryon in $ Ξ_c$ channel. Comparison of the obtained results with the experimental data suggests assignment of $Ξ_c(2930)$ state as the angular excitation of the ground state $Ξ_c$ baryon with quantum numbers $J^P=\frac{1}{2}^{-}$.

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arXiv2018

Interpretation of the newly discovered $Ω$(2012)

Very recently Belle Collaboration reported observation of a narrow state called $Ω(2012)$ with mass $2012.4 \pm 0.7$~(stat)~$\pm 0.6$(syst)~MeV and width $6.4^{+2.5}_{-2.0}$~(stat)~$\pm 1.6$~(syst)~MeV. We calculate the mass and residue of $Ω(2012)$ state by employing the QCD sum rule method. Comparison of the obtained results with the experimental data allows us to interpret this state as $1P$ orbital excitation of the ground state $Ω$ baryon, i.e. with quantum numbers $J^P=\frac{3}{2}^-$.

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